In November of 1978 the Occupational Safety and Health Administration received a complaint from an employee who stated that he was suffering from a brain tumor and knew of other with the same problem. This spurred a series of epidemiological investigations to determine whether this was a random occurrence or whether these tumors might be related to worker exposure to toxic substances at the plant. At the one facility in question, 18 brain cancer deaths have occurred to date and 25 other cases have been indentified at another plant; similar cases are being reported in petrochemical facilities in other parts of the world. It is our intention to bring together scientists from government, industry, academic institutions and labor to review the current state of the knowledge concerning occupational and environmental etiology of brain tumors. The consideration of currently available data will allow dissemination of state-of-the-art information to researchers throughout the world. It will further serve to assist in evaluation of etiological factors, of particular significance now as measures are considered for control of the problem.